Active acoustic metamaterials using sensor-driver architecture

Abstract

Acoustic metamaterials can, in principle, overcome the fundamental limitations of passive structures and can enable novel applications that are hard or impossible with passive media. However, active acoustic metamaterials remain elusive, and the few implementations going beyond basic material parameter tunability lag significantly behind the true potential of active media. We will present a design method that results in active metamaterials whose acoustic response is electronically programmed to cover a very large range of non-linear acoustic responses. Specifically, metamaterials obtained with this approach can be configured to have almost any second and higher harmonic response, making them very effective and versatile non-linear acoustic media. We demonstrate experimentally this design methodology in an application in which an acoustically thin metamaterial funnel responds to incident sound waves by producing collimated second harmonics. Past demonstrations of this type of active metamaterials will also be briefly reviewed.